The invention relates to a roll press for the compression or compacting of granular products, having two mobile rolls, separated by a roll gap, which respectively are mounted rotatably in a machine frame by means of a shaft and are driven in opposite directions, wherein the shafts of the mobile rolls are accommodated in bearing housings arranged movably in the machine frame, and wherein respectively two bearing housings of different rolls, arranged on one side of the rolls, are interconnected by means of at least one pressure cylinder having at least two working chambers, and further relates to a method for centering mobile rolls in a roll press of the abovementioned type.
For the centering of rolls in roll presses for the compression or compacting of granular products, the rolls are generally held in their desired position by large-sized hydraulic drives in order that, on the one hand, the pressure in the roll gap between the rolls is maintained and, on the other hand, as a result of the centering, the parallelism of the limit of the roll gap is maintained by the surface of the rolls. In this centering, the hydraulic drives operate at high force both to maintain the parallelism of the roll gap and to maintain the pressure in the roll gap. To this end, in the simplest case, a first roll is mounted as a fixed roll immovably in bearings which, for their part, are fastened to extension arms by bearing housings in a machine frame. By contrast, a second roll is mounted as a mobile roll in bearings which are disposed in bearing housings arranged movably between two extension arms of the machine frame. The hydraulic drives for the relative positioning of the mobile roll in relation to the fixed roll and for the maintenance of the pressure in the roll gap exert high forces upon the machine frame as a counter bearing, for which purpose it is necessary to design the machine frame in correspondingly stable configuration.
In roll presses having rolls of sometimes far more than 50 tonnes in weight, a correspondingly large dimensioning of the machine frame is necessary, so that the logistics of the machine frame and its handling whenever the rolls need, in turns, to be changed, is complex, and is only possible with correspondingly large-sized cranes and removal aids.
In order to reduce the overall dimensions of the necessary dimensioning of the machine frame, in DE 10 2006 006 090 it is proposed to configure both rolls of the roll press as a mobile roll, these two mobile rolls being interconnected by means of the bearings and the bearing housings and by means of hydraulic drives. The rolls, the bearings, the bearing housings and the hydraulic drives here form a closed system of forces, which relieves the machine frame of load with the result that this can be dimensioned in smaller overall size. This arrangement has proved itself in practice. In order to change the rolls, it is necessary, however, to dismantle the machine frame and separate the bearing housings from the pressure cylinders. Since the pressure cylinders are part of a closed system of forces, a free suspension of the heavy pressure cylinders is necessary, the result of which is that the hydraulic lines must be flexible hoses. In order to keep the viscosity-dictated resistance of the pressure medium when flowing through the lines as low as possible, it is also necessary to keep the flexible lines short. When dismantling the roll press, it is thus necessary to separate the very heavy pressure cylinder, which is solely part of the abovementioned closed system of forces, from the fixed pump, in which case the hydraulics, namely pumps, lines and cylinders, have to be again refilled and deaerated when put back together. The effort involved in changing the rolls is hence relatively high, whereby the costs of the roll change are higher than in roll presses having a mobile and a fixed roll.